Question

7 pens and 8 pencils together costs Rm 32.50. If 6 pens and 4 pencils together costs rm 25. How much costs for 2 pencils?

Answer 1

cost of pen = x                                        

cost of pencil = y   

7x + 8y =  32.50 ..................eq [1]

6x + 4y = 25 ....................... eq[[2]

7x + 8y = 32.50

12x + 8y = 50   multiply eq [2] by 2

now subtract eq [2] from eq [1]

  7x   + 8y =32.50

12x  + 8y = 50

[-]__ [-]____[-]______

-5x    0       -17.5

________________

-5x = -17.5

x = 3.5 Cost of one  pen is Rs 3.5

Put values of x in eq 2

6x + 4y = 25

3.5×6 + 4y = 25

21 + 4y = 25

4y = 4

y = 1  Cost of one pencil is Rs 1

Cost of 2  pencil is  Rs 2 ANS

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